Disclamer: I'm working on the Fixed Wireless products for Telenor (Zyxel NR7101 outdoor wall mounted unit). Not the Mobile Broadband products. We are working with Zyxel and Qualcom to try and implement an upstream queue which adapts to available radio resources. To much NDA so can't really disclose anything useful. Lets just say we are aware of the issues and are actively working to try and improve the situation - but don't hold your breath for a sollution.
What sort of HW are you running your LTE on?
Do you have a subscription with rate limitations? The PGW (router which enforces the limit) is a lot more latency friendly than if you are radio limited. So it may be beneficial to have a "slow" subscription rather than "free speed" then it comes to latency. Slow meaning lower subscrption rate than radio rate.
Also would be interesting to see separate tests for upstream and downstream, as the issues and implementations are different in each direction.
-Erik